Once you’ve decided on a wind turbine, your next choice is the type and height of tower. For best production, the turbine should be on a tall tower to maximize wind speed and minimize turbulence, but there are other factors that can affect your tower choice:
Economics & Aesthetics. The three basic tower types to consider are tilt-ups, guyed lattice, and freestanding. Most tilt-ups are made of pipe or tube and require guy wires for support. They are assembled on the ground and raised into position with a winch or tow vehicle. For turbines with a rotor diameter of 12 feet or less, this tower is usually the lowest-cost option. Guyed lattice towers are constructed on the ground and raised with a crane or assembled vertically, one section at a time, with a process known as stacking. These towers are mostly used for turbines with rotor diameters less than 25 feet and are the lowest-cost fixed tower option. Freestanding towers fall into two categories: self-supporting lattice and monopole. The self-supporting lattice tower is usually assembled on the ground and raised with a crane. These towers are typically used for turbines with a rotor diameter of 20 feet or more and require a fairly large foundation, making this option fairly expensive. Monopole towers are available for most turbine sizes and tilt-up versions are becoming more common. Although many people prefer the aesthetics of a monopole, these towers require the largest foundation of all and are usually the most expensive option.
Building codes & zoning regulations. Local building codes may dictate using a heavier tower and larger foundation than expected. Zoning regulations may limit you to a specific tower type or tower height, or impose other requirements that will affect project economics.
Engineering. Turbines exert many complex forces on the tower and its foundation. The larger the turbine, the more robust the tower and foundation need to be. The turbine, tower, and foundation function as a system, and need to be engineered to work together. Most turbine manufacturers offer or recommend an appropriate tower for their turbines.
Site conditions. Soil type affects foundation design and may limit tower options. Soft soil or bedrock tends to require more robust foundations than “average” soil. Uneven terrain can be a determining factor as well.
Site access is frequently overlooked. Can the site accommodate very heavy-wheeled equipment, such as a crane and concrete delivery truck? If it can’t, then your tower options are quite limited.